Prosecutor Charles Row said Duffety “appeared to have no sexual boundaries”.

“He was completely unapologetic.

“Despite talking to him, nothing seemed to change his behaviour.”

The court heard that Duffety was just 13 years old when he forced a boy to perform oral sex in exchange for playing Snake on his mobile phone.

The court heard he timed his victim with a stopwatch and, the longer the abuse went on, the more time the youngster was given to use the phone.

The incident was investigated by police at the time but the case was dropped after Duffety denied all wrongdoing.

Last January, however, Duffety was accused of exposing himself to a girl and forcing her to touch his genitals.

The incident is believed to have occurred before November 2015, but the girl delayed reporting it to police after Duffety threatened to break her neck if she told anyone.

As part of their investigation, police seized the defendant’s phone and found 146 indecent images of children stored on it.

There was also evidence the defendant, who at the time was working as a swimming instructor at Horfield Leisure Centre, had disclosed his perverted sexual desires online.

Judge William Hart jailed Duffety for five years, with three further years on extended licence.

The former swimming instructor, who was employed by leisure centre operator Everyone Active at the time of his arrest, was made the subject of a sexual harm prevention order, which is designed to prohibit contact with children under the age of 16.